1,311 research outputs found

    Stress biomarker changes following a series of repeated static and dynamic apneas in non-divers

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    Purpose This study examined the magnitude of physiological strain imposed by repeated maximal static and dynamic apneas through assessing a panel of stress-related biomarkers. Methods Eleven healthy men performed on three separate occasions (≥72-h apart): a series of five repeated maximal (i) static (STA) or (ii) dynamic apneas (DYN) or (iii) a static eupneic protocol (CTL). Venous blood samples were drawn at 30, 90, and 180-min after each protocol to determine ischaemia modified albumin (IMA), neuron-specific enolase (NSE), myoglobin, and high sensitivity cardiac troponin T (hscTnT) concentrations. Results IMA was elevated after the apnoeic interventions (STA,+86%;DYN,+332%,p ≤ 0.047) but not CTL (p = 0.385). Myoglobin was higher than baseline (23.6 ± 3.9 ng/mL) 30-min post DYN (+70%,38.8 ± 13.3 ng/mL,p = 0.030). A greater myoglobin release was recorded in DYN compared with STA and CTL (p ≤ 0.035). No changes were observed in NSE (p = 0.207) or hscTnT (p = 0.274). Conclusions Five repeated maximal DYN led to a greater muscle injury compared with STA but neither elicited myocardial injury or neuronal-parenchymal damage

    Opportunities and roadblocks in the decarbonisation of the global steel sector: A demand and production modelling approach

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    International audienceThe steel sector represents a growing share of global carbon dioxide (CO 2) emissions and is perceived as a hardto-abate sector in the drive towards economy-wide decarbonisation. We present a model detailing steel demand and multiple steel production pathways within a larger global multi-regional energy system simulation model, projecting material, energy and emissions flows to 2100. We examine decarbonisation levels and options under different assumptions on climate policy, technologies and steel demand patterns, and study low-carbon options in the production of hydrogen as a steel decarbonisation vector. Global steel demand increases at a decelerated pace compared to the past two decades (+65 % in 2050 compared to 2020), driven by substantial increases in the underlying socioeconomic conditions. Climate policies lead to a limited positive feedback effect on steel demand (+21 % in 2050) due a faster equipment turnover and higher electrification, which could be overcompensated by energy saving and material efficiency measures. Increased recycling and strong electrification (up to 63 % of production in 2050) are projected as key levers towards decreasing emissions, made possible thanks to the increasing availability of steel scrap. Strong climate policies would be needed to push the steel sector to decarbonise fully, with electrification, carbon capture, biomass and hydrogen all contributing. Carbon capture would be necessary to reach net-zero emissions in the second half of the century

    Experimental and theoretical investigation of the mechanism of the reduction of O2 from air to O22– by VIVO2+–N,N,N-amidate compounds and their potential use in fuel cells

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    The two-electron reductive activation of O2 to O22– is of particular interest to the scientific community mainly due to the use of peroxides as green oxidants and in powerful fuel cells. Despite of the great importance of vanadium(IV) species to activate the two-electron reductive activation of O2, the mechanism is still unclear. Reaction of VIVO2+ species with the tridentate-planar N,N,N-carboxamide (ΗL) ligands in solution (CH3OH:H2O) under atmospheric O2, at room temperature, resulted in the quick formation of [VV(═O)(η2-O2)(κ3-L)(H2O)] and cis-[VV(═O)2(κ3-L)] compounds. Oxidation of the VIVO2+ complexes with the sterically hindered tridentate-planar N,N,N-carboxamide ligands by atmospheric O2 gave only cis-[VV(═O)2(κ3-L)] compounds. The mechanism of formation of [VV(═O)(η2-O2)(κ3-L)(H2O)] (I) and cis-[VV(═O)2(κ3-L)] (II) complexes vs time, from the interaction of [VIV(═O)(κ3-L)(Η2Ο)2]+ with atmospheric O2, was investigated with 51V, 1H NMR, UV–vis, cw-X-band EPR, and 18O2 labeling IR and resonance Raman spectroscopies revealing the formation of a stable intermediate (Id). EPR, MS, and theoretical calculations of the mechanism of the formation of I and II revealed a pathway, through a binuclear [VIV(═O)(κ3-L)(H2O)(η1,η1-O2)VIV(═O)(κ3-L)(H2O)]2+ intermediate. The results from cw-EPR, 1H NMR spectroscopies, cyclic voltammetry, and the reactivity of the complexes [VIV(═O)(κ3-L)(Η2Ο)2]+ toward O2 reduction fit better to an intermediate with a binuclear nature. Dynamic experiments in combination with computational calculations were undertaken to fully elucidate the mechanism of the O2 reduction to O22– by [VIV(═O)(κ3-L)(Η2Ο)2]+. The galvanic cell {Zn|VIII,VII||Id, [VIVO(κ3-L)(H2O)2]+|O2|C(s)} was manufactured, demonstrating the important applicability of this new chemistry to Zn|H2O2 fuel cells technology generating H2O2 in situ from the atmospheric O2

    The performance of banks in the Czech Republic in 2019-2021 in relation to windfall profits tax

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    This thesis examines the performance of six banks that were subject to the windfall profits tax in the Czech Republic in 2022 and follows the years 2019 to 2021 when the banks were affected by the covid-19 pandemic. The thesis describes the situation in these years in general, the fiscal and monetary policy response, and the theoretical concept of the windfall tax. Subsequently, an analysis of their balance sheets and profit and loss statements is conducted and compared with the performance of the banking sector in the country. Finally, the paper concludes by estimating the Windfall Profits Tax yield using two methods.Tato diplomová práce se zabývá hospodařením šesti bank, na které byla v České republice uvalena v roce 2022 daň z mimořádných zisků a sleduje roky 2019 až 2021, kdy byly banky zasažené pandemií covidu-19. V práci je obecně popsána situace v těchto letech, reakce fiskální a monetární politiky a teoretický koncept Windfall tax. Následně je provedena analýza jejich rozvah, výkazů zisků a ztrát a jejich srovnání s výsledky bankovního sektoru v ČR. Na závěr práce je dvěma metodami odhadnut výnos z daně z mimořádných zisků

    Power Efficient Machine Learning Models Deployment on Edge IoT Devices

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    Computing has undergone a significant transformation over the past two decades, shifting from a machine-based approach to a human-centric, virtually invisible service known as ubiquitous or pervasive computing. This change has been achieved by incorporating small embedded devices into a larger computational system, connected through networking and referred to as edge devices. When these devices are also connected to the Internet, they are generally named Internet-of-Thing (IoT) devices. Developing Machine Learning (ML) algorithms on these types of devices allows them to provide Artificial Intelligence (AI) inference functions such as computer vision, pattern recognition, etc. However, this capability is severely limited by the device’s resource scarcity. Embedded devices have limited computational and power resources available while they must maintain a high degree of autonomy. While there are several published studies that address the computational weakness of these small systems-mostly through optimization and compression of neural networks- they often neglect the power consumption and efficiency implications of these techniques. This study presents power efficiency experimental results from the application of well-known and proven optimization methods using a set of well-known ML models. The results are presented in a meaningful manner considering the “real world” functionality of devices and the provided results are compared with the basic “idle” power consumption of each of the selected systems. Two different systems with completely different architectures and capabilities were used providing us with results that led to interesting conclusions related to the power efficiency of each architecture

    Energy-economy implications of the Glasgow pledges: a global stocktake of COP26

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    The 2015 Paris Agreement establishes a framework in which countries submit their policy targets to the United Nations Framework Convention on Climate Change (UNFCCC) and further invites parties to submit long-term low greenhouse gas (GHG) emission development strategies. In this paper, we take stock of recent updates in the nationally determined contributions (NDCs) and long-term low greenhouse gas (GHG) emission development strategies (LTS) announced leading up to and during the Conference of the Parties (COP 26) in Glasgow, in November 2021. We focus on the transition of G20 countries, which accounted for nearly 75% of global GHG emissions since 1990, assessing three different scenarios: (i) current policies; (ii) announced policy targets (NDC-LTS); and (iii) a 1.5°C-compatible pathway. We further analyse decarbonisation drivers and energy system transformation metrics within each scenario, highlighting both the policy options to bring emissions in line with ambitious climate targets, and the associated labour market transition. The regional focus reveals heterogeneous decarbonisation pathways, mitigation options and emission gaps, informing the ongoing first “global stocktake” under the Paris Agreement. Delivering on both NDC and LTS targets could limit the temperature increase of global mean temperature to about 1.8°C above pre-industrial levels by the end of the century, reducing the ambition gap in the long run. The results furthermore suggest that the scale and concentration of cross-sectoral employment transition could warrant careful attention when designing policies to close the remaining implementation gap between current policies and climate targets

    Design and modulation of selectivity toward vanadium(V) and uranium(VI) ions: coordination properties and affinity of hydroxylamino-triazine siderophores

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    Based on the strong binding and high selectivity properties of 2,6-bis[hydroxy(methyl)amino]-4-morpholino-1,3,5-triazine (H2bihyat) for [UVIO2]2+, novel binucleating ligands (BLs) N,N′,N″,N‴-((1,4-phenylenebis(oxy))bis(1,3,5-triazine-6,2,4-triyl))tetrakis(N-methylhydroxylamine) (H4qtn), N1,N4-bis(4,6-bis(hydroxy(methyl)amino)-1,3,5-triazin-2-yl)benzene-1,4-diamine (H4pdl), and N1,N2-bis(4,6-bis(hydroxy(methyl)amino)-1,3,5-triazin-2-yl)ethane-1,2-diamine (H4enl) were synthesized. Binuclear complexes formed by coordination of hard metal ions with H4qtn are thermodynamically more stable than their mononuclear analogues with H2bihyat due to the increase in entropy accompanying the formation of more chelate rings. Reaction of either H4qtn or H4pdl or H4enl with [UVIO2]2+ and [VVO2]+ resulted in the isolation of the binuclear complexes [(UVIO2)2(μ-qtn)(H2O)4] (1), [(VVO2)2(μ-qtn)][PPh4]2[PPh4] (2), [(UVIO2)2(μ-pdl)(H2O)2(MeOH)2] (3), [(VVO2)2(μ-pdl)][PPh4]2 (4), [(UVIO2)2(μ-enl)(H2O)4] (5), and [(VVO2)2(μ-enl)][PPh4]2 (6). The binuclear complexes 1–6 were characterized by single-crystal X-ray diffraction analysis in solid state and by NMR and ESI-MS in solution. The comparison of the coordination ability of the BLs with either pyridine-2,6-dicarboxylic acid (H2dipic) or H2bihyat or CO32– toward [UVIO2]2+ and [VVO2]+ was investigated by NMR and UV–vis spectroscopies and DFT theoretical calculations, revealing a superior performance of BLs. The selectivity of the BLs for [UVIO2]2+ over [VVO2]+ is decreased compared to that of H2bihyat but increases considerably at pH > 9 values. Formation of the mixed-metal binuclear species [UVIO2(μ-O)VVO2] influences the selectivity and dynamics of the reaction of H4qtn for [UVIO2]2+ and [VVO2]+ in aqueous solution. The results of this study provide crucial information for the ligand design and the development of stronger and more selective systems
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